login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A077776 Palindromic wing primes (a.k.a. near-repdigit palindromes) of the form (10^a(n)-1) - 8*10^[ a(n)/2 ]. 1
3, 11, 27, 87, 339, 363, 3159, 36155, 45305, 314727 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Prime versus probable prime status and proofs are given in the author's table.

REFERENCES

C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.

LINKS

Table of n, a(n) for n=1..10.

Patrick De Geest, World!Of Numbers, Palindromic Wing Primes (PWP's)

Makoto Kamada, Prime numbers of the form 99...99199...99

Index entries for primes involving repunits.

FORMULA

a(n) = 2*A183184(n)+1.

EXAMPLE

a(n)=27 -> (10^27-1)-8*10^13 = 999999999999919999999999999.

MATHEMATICA

Do[ If[ PrimeQ[10^n - 8*10^Floor[n/2] - 1], Print[n]], {n, 3, 1000, 2}] (* Robert G. Wilson v, Dec 16 2005 *)

CROSSREFS

Cf. A004023, A077775-A077798, A107123-A107127, A107648, A107649, A115073, A183174-A183187.

Sequence in context: A059400 A250223 A250271 * A113836 A036571 A003060

Adjacent sequences:  A077773 A077774 A077775 * A077777 A077778 A077779

KEYWORD

more,nonn,base

AUTHOR

Patrick De Geest, Nov 16 2002

EXTENSIONS

Added one more term from PWP table, by Patrick De Geest, Nov 05 2014

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified September 23 20:33 EDT 2017. Contains 292391 sequences.